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//===--- ARMComputeBlockSize.cpp - Compute machine block sizes ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBasicBlockInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include <vector>
using namespace llvm;
namespace llvm {
// mayOptimizeThumb2Instruction - Returns true if optimizeThumb2Instructions
// below may shrink MI.
static bool
mayOptimizeThumb2Instruction(const MachineInstr *MI) {
switch(MI->getOpcode()) {
// optimizeThumb2Instructions.
case ARM::t2LEApcrel:
case ARM::t2LDRpci:
// optimizeThumb2Branches.
case ARM::t2B:
case ARM::t2Bcc:
case ARM::tBcc:
// optimizeThumb2JumpTables.
case ARM::t2BR_JT:
case ARM::tBR_JTr:
return true;
}
return false;
}
void computeBlockSize(MachineFunction *MF, MachineBasicBlock *MBB,
BasicBlockInfo &BBI) {
const ARMBaseInstrInfo *TII =
static_cast<const ARMBaseInstrInfo *>(MF->getSubtarget().getInstrInfo());
bool isThumb = MF->getInfo<ARMFunctionInfo>()->isThumbFunction();
BBI.Size = 0;
BBI.Unalign = 0;
BBI.PostAlign = 0;
for (MachineInstr &I : *MBB) {
BBI.Size += TII->getInstSizeInBytes(I);
// For inline asm, getInstSizeInBytes returns a conservative estimate.
// The actual size may be smaller, but still a multiple of the instr size.
if (I.isInlineAsm())
BBI.Unalign = isThumb ? 1 : 2;
// Also consider instructions that may be shrunk later.
else if (isThumb && mayOptimizeThumb2Instruction(&I))
BBI.Unalign = 1;
}
// tBR_JTr contains a .align 2 directive.
if (!MBB->empty() && MBB->back().getOpcode() == ARM::tBR_JTr) {
BBI.PostAlign = 2;
MBB->getParent()->ensureAlignment(2);
}
}
std::vector<BasicBlockInfo> computeAllBlockSizes(MachineFunction *MF) {
std::vector<BasicBlockInfo> BBInfo;
BBInfo.resize(MF->getNumBlockIDs());
for (MachineBasicBlock &MBB : *MF)
computeBlockSize(MF, &MBB, BBInfo[MBB.getNumber()]);
return BBInfo;
}
} // end namespace llvm
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